The present invention relates to a method of manufacturing a semiconductor device, and more specifically to a method of manufacturing a semiconductor device, which uses a chemical-mechanical polishing (to be called simply CMP hereinafter) technique.
Recently, as the density of semiconductor device is increased and the size thereof is reduced, various types of micromachining techniques are being researched and developed. The CMP technique is one of these micromachining technique, and is essential for the smoothing of interlayer insulation films, the formation of plugs and embeded metal wires, and the formation of embeded element separation regions.
Usually, the CMP method is used to smooth an uneven surface; however the method can be applied to other usage. For example, with the CMP method, it becomes possible to form a metal film selectively on the bottom surface and side walls of a recessed portion of a substrate, into a shape corresponding to that of the recessed portion.
More specifically, a metal film is formed on a substrate having a recessed portion, in a shape which reflects the configuration of its surface. Then, the surface of the substrate on which the metal film is formed, is polished by the CMP method. The polishing process is stopped when the entire portion of the metal film formed on the substrate, except for that remaining in the recessed portion, is removed. In this manner, the metal film is formed selectively only on the bottom surface and side walls of the recessed portion.
However, in the case where the CMP method is applied to the above-described usage, the following problem occurs. That is, with the above-described method, the surface of the substrate, subjected to CMP is not completely smooth, but some recessed portions still remain. As a result, dusts such as polisher used for the CMP and fine particles created by the CMP adhere to the bottom surfaces and side walls of the recessed portions, or fill the recessed portions, while polishing the metal film formed on the surface of the substrate.
In the case where the next step is started in this status, the reliability and yield of the element are naturally decreased. In order to avoid this, the dust should be eliminated after the CMP is finished. However, in the case where, particularly, the opening diameters of the recessed portions are in the order of sub-microns, it is very difficult to completely remove the dust even if the washing is performed after finishing the CMP.